With its solar panels, super insulation and electric car in the drive, you can't help but feel impressed by Bill and Sue Dunster's home. Just imagine - hot water from sunshine, your electricity nearly free. And they make it sound so easy. "None of this stuff is special at all," says Bill, his hand sweeping around their modest living area. "It's completely mundane; we're trying to define the new ordinary."

Yeah, right, you find yourself thinking - what about real people in the real world? Those in flats with rattly windows, or a draughty modern semi where the heat goes up the chimney?

But Dunster argues that his ideas are for everyone. As an architect who has championed sustainable living since his student days, he says we can massively reduce our impact on the planet through a combination of energy conservation and domestic power production. The problem, he claims, is information - people realising what their options are. There are mini wind turbines you can bolt on to your roof like a satellite dish, for example, yet you won't find these at the DIY store. And any electrician should be able to wire up a solar panel. Another issue is cost: whether it's organic veg or solar panels, it has never been cheap to be green.

To this end, the Dunsters are putting together a list of energy-generating equipment, which, they promise, will not only demystify the technology, but also make it more affordable for the ordinary person. By guaranteeing suppliers a certain quantity of orders through their website, they have convinced them to slash prices. And don't be put off by the idea that you have to go from slobby consumer to saviour of the planet in one go. Anyone interested in leading a more sustainable life should be happy to do it by increments, not try to be perfect straight away. Heck, says Dunster, they're still saving up for a low-energy light circuit.

Being realistic, he says, about £25,000 should easily pay for your house to become "carbon neutral", generating a substantial amount of its own power and cutting out its contribution to greenhouse gases. Hardly a bargain, but neither is it a silly figure when you consider what people will spend on a conservatory or car.

The Dunster's "new ordinary" was conceived 10 years ago on a plot of land next to the river Thames, in south-west London. There was no fancy budget - they did some of their own labouring and roped in friends to help with decoration. Neither was there an assumption that everything would go smoothly first time round. They got the underfloor heating wrong in the living area (turns out they didn't need it) and are still saving up for a posh hot water tank that's compatible with their wood-fired stove. "This house is like a test rig, so before we inflict our ideas on others, we're finding out what works," says Bill.

The house is three-storeys, with that trademark Dunster feature - a full-height conservatory - on its south side. This has several functions. First, it contains the photovoltaic cells that convert sunlight into electricity, and the solar hot water tubes. It also, says Dunster, provides extra living space for about 85% of the year. Finally, simply by opening and closing windows between the main house and the conservatory, or the conservatory and the outside, the Dunsters can regulate the temperature of the whole place - warm air from the sun for heating; fresh air for ventilation.

The main living space is on the first floor, which you reach from the street via a gangway fashioned from recycled steel. Many parts of their home are made from reclaimed materials, or at the very least have been locally sourced to minimise transport pollution. "The house is built with all the standard things you get from builders' merchants," says Dunster. "There's nothing clever about it."

In the living area you get an idea of what he means. There are bog-standard terracotta tiles on the floor and the stove (the house's main heat source) is a simple wood-burning model you'll pick up for around £400 and is new enough to meet clean air standards. Eventually, when the Dunsters can afford that water tank, it will supplement the solar hot water as well as heat the living space in winter. There's nothing clever about keeping in this heat, either. It's just down to closing doors after you, so the warmth doesn't escape outside. That, and insulation, insulation, insulation.

The Dunsters' walls, floors and roof have at least 150mm-thick insulation, which makes the house so thermally efficient that no heating is needed in the top-floor bedrooms. These are kept warm by a combination of solar gain - sunlight through two sets of windows - and hot air that rises up from the conservatory or escapes from the living areas below. "We've cracked our heating needs," says Bill. "Now we need to do the same with our electricity."

Soon, he says, he will connect one of a new generation of mini wind turbines to the roof. This will be no more unsightly than a TV satellite dish and should bring them closer to providing all their electricity needs.

Bill has spent all his professional life exploring sustainable living. As a student at Edinburgh University in the early 1980s, he designed an imaginary housing estate run on solar power. ("They thought I was nuts," he says of his tutors.) While he must have often felt he was a voice in the wilderness, 20 years later this dream became a reality when he completed Britain's first "green" housing scheme, a development of 82 homes in south London known as BedZed.

BedZed is a "zed", or zero energy development, whereby homes reduce their heat and power needs by so much that they can rely on renewable resources. There are photovoltaic cells to generate electricity, while an on-site combined heat and power plant, run on willow coppice, provides extra power needs. There is a "green" water-treatment works, an electric car pool, roof gardens and terraces for the residents. With its timber cladding, sedum roofs and, yes, southerly aspect conservatories, the development is attractive to look at, too.

Despite high praise from architects, environmentalists and the public (these places have proved a sound investment for residents), Dunster has failed to get his ideas adopted by mainstream home builders. It's a big frustration. Developers are resistant because of the extra cost of zed homes. If only they would build his designs on a large enough scale, however, prices would come down; 5,000 units should do it, but can he persuade the Office of the Deputy Prime Minister to go for it? No chance.

It's at moments like this that you really have to admire Dunster's perseverance. He could sit back and design one-off homes, safe in the knowledge that he proved himself with BedZed. But no, he's thinking about the implications of house building on the planet's future.

In 2006, he says, demand for oil will outstrip supply, and that can only mean more conflicts over a dwindling resource. "Everything is dependent on fossil fuels," he argues. "This is not a safe place to be for the human race. It's not rational behaviour." And with it now being widely accepted that the consumption of fossil fuels is affecting climate, that gives you two good reasons to scale back demand for oil and gas. One obvious way to do this is to have housing that requires a minimal amount of these resources.

Now, says Dunster, a new factor has crept into the equation. Recently, the government has begun to flirt with restarting the nuclear power programme to meet electricity needs. This, he thinks, is bonkers. "If the government is to meet its 60%carbon-reduction targets by 2050, the only things you can do is either what the French have done and go nuclear or invest in the less glamorous idea of energy conservation and micro power generation."

What Dunster shows us is that micro power generation - each of us creating our own power supply - is possible and within reach. It's no accident that the Dunster's home is named Hope House. "These issues are bigger than electricity," he says. "It's about stopping big business from investing in a dangerous technology with a dreadful long-term legacy. For the first time it's the little people who can make a very big difference."

Haven't got the energy? Think again

Imagine a world with no electricity bills and bargain hot water ... er, on tap. It's enough to make any eco-sceptic rush out and buy a wind turbine. If it weren't for the initial outlay, that is: a solar hot-water system can set you back £15,000. With this in mind, Bill Dunster is offering discount renewable-energy gear on his website (zedfactory.com). Here's what he reckons you'll need to supply a three-bed household with all its energy needs:

Wind and solar electricity

Assuming you use low-energy lighting, A-rated white goods and give up the power shower, you'll need one wind turbine and 20 solar electric panels (photovoltaic cells). Allow just over £1,000 for the turbine and around £5,000 for the panels. You can plug the turbine into the mains, though you might need help fixing it to the roof. The panels need either a very keen DIY-er or an expert to install them (details on Dunster's website).

Solar hot water system

Basically a set of tubes on your roof, filled with water which heats in the sunlight. This, in turn, warms your household water via a heat exchanger. A system that includes a special hot water tank will set you back £4,200, including installation. The system works well in spring, summer and autumn, but in winter you'll need to top it up with hot water from the ...

Central heating pellet boiler

Pellets are the offal of the timber industry: poor-quality thinnings and compressed wood shavings. You'll have little change from £6,000 for one of these systems, though, compared with the cost of a standard boiler, it doesn't seem that bad. You'll need to fill it with pellets: if you want something that fills itself automatically, expect to pay an extra £5,000.

On the road: biodiesel or electric cars

There are purpose-built electric cars such as the G-wiz (from £7,599, 020-8574 3232; goingreen.co.uk), while giants such as Citroën have electric versions of their models, but these drive for only around 60 miles before they need a recharge. An alternative is to run a car on biodiesel, which is basically vegetable oil or filtered chip fat.

One problem is finding a filling station (try biodieselfillingstations.co.uk), but you can always use regular diesel if you run out. To convert a diesel VW Lupo, for example, costs around £1,350.